At what rate will 1400 naira

yield naira 900 in 3yrs 9 months

1 answer

Depends what type of interest you want:

simple interest (usually not used for times greater than one year) :
I = PRT
900 = (1400)(R)(15/4)
3600 = 21000R
R = .1714.. , so appr 17.1% per annum

compound interest:
i = ?
n = 45 , (3 years and 9 months = 45 months)

2300 = 1400(1+i)^45
1.64285... = (1+i)^45
take 45th root
1.011093 = 1+i
i = .011093 per month
12i = .13312

The rate is 13.3% per annum compounded monthly